Tracking individual cells within the lung as they move around and multiply has given Duke University researchers new insights into the causes of idiopathic pulmonary fibrosis (IPF) a disease that can only be treated now by lung transplantation. IPF fills the delicate gas exchange region of the lung with scar tissue, progressively restricting breathing. The Duke University Medical Center researchers have discovered that some commonly held ideas about the origins of the scar-forming (fibrotic) cells are oversimplified, if not wrong. “We are the first to show that pericytes, a population of cells previously described to play a role in the development of fibrosis in other organs, are present in fibrotic lung tissue,” said Dr. Christina Barkauskas, a pulmonary fellow in the Duke Division of Pulmonary, Allergy, and Critical Care Medicine. The team found that pericytes move from blood vessels into fibrotic regions, and were in the damaged lungs of both humans and mice. In mice, they also showed that the epithelial cells, which make up the lacy sacs called alveoli, could divide and repair the damage in the gas-exchange location, but these cells were not the source of scarring. IPF affects about 100,000 people in the U.S. each year and leads to death within three years of diagnosis. The study was published online on November 28, 2011 in PNAS. “We don’t know yet whether the pericytes make the scar matrix itself or just release signals that stimulate the scarring process, but either way, they are a potential target for new therapies,” said Dr. Brigid Hogan, senior author and chair of the Duke Department of Cell Biology. The researchers used genetic lineage tracing to study the origin of cells that gathered in fibrotic areas. They gave several different cell types an indelible fluorescent tag and then followed the cells over time.